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Publicly Available Published by De Gruyter July 1, 2012

Piriformis muscle injection guided by sciatic nerve stimulation: Quick, simple, and safe technique

  • M. Mayo-Moldes EMAIL logo , A. Carregal , M. Corujeira , T. Fernandez and V. Vilanova

To the Editor,

The Piriformis syndrome (PS) is thought to involve the piriformis muscle because of its proximity to the sciatic nerve. This muscle follows a linear path coinciding with the sciatic nerve which lies beneath the muscle in the parasacral region [1].

PS is associated with buttock, hip and lower limb pain. Medical treatment that has been applied includes therapeutic stretching, ultrasound, massage, oral analgesics and intramuscular local anesthetic with or without steroid injections [2].

There is not a universally accepted technique for injection of the piriformis muscle. Several authors have reported imaging-guided injection techniques with fluoroscopy or CT that may not be available in most pain management centers [3,4]. Nowadays, ultrasound has shown promise for pain. However, the technique requires some experience before it can be performed by one operator also handling the needle [5,6].

We investigated whether local anesthetic nerve-stimulator guided injections are effective in achieving long-lasting pain relief in (PS) because the nerve stimulation is widely available, radiation free and easy to use.

Weprospectively enrolled 100 patients diagnosed of PS. All subjects complained of buttock, hip and lower limb pain for 3 months duration before admission to the study and all of them were refractory to conservative management measures. Pain was aggravated by sitting, stair climbing, and leg crossing. Subjects were excluded if imaging studies demonstrated evidence of a herniated lumbar disk or nerve root impingement, or electromyography examination demonstrated pathology proximal to the sciatic.

We use standard surface landmarks for the posterior approach to sciatic blockade. (After a skin wheal of local anesthetic), a 21G × 100 mm Stimuplex needle (Pajunk) was inserted perpendicular to the skin and advanced with an initial setting of 1.5 mA, 2 Hz. The sciatic nerve is identified by a reduction of frank gluteal contraction and plantar flexion/dorsiflexion response at a current of 1mA. We then retract the needle till extinction of the response.

Two patients did not meet our study criteria, and four patients refused to participate. Thus, 94 patients (70 females and 24 males) were enrolled in the study after applying exclusion criteria. The average age of the patients was 50 years. A perisciatic injection of local anesthetic using a nerve stimulator to locate and inject near the sciatic nerve and into the piriformis muscle was performed. All patients received 10 ml bupivacaine 0.125% without addition of steroids and were clinically evaluated at 1 and 4 weeks after the procedure. The visual analogue scale (VAS) was used to evaluate treatment response (VAS: 0 = no pain; 100 = worst possible pain). Prior to data analysis, improvement greater than 25mmon the VAS score was selected as clinically significant.

Data are shown as the mean ± standard deviations. Data were evaluated using paired t test. P < 0.05 was required for significance. We used SPSS 11 (SPSS Inc., Chicago, IL) for data analysis.

There was a statistically significant reduction in mean VAS scoring for buttock and hip pain at week 1 (84%) and week 4 (70%) (Fig. 1) and the pain was improved from 66.5±16.1mmto 32.8±27.3mm at the 4-week follow-up visit. 70% of patients experienced full recovery and were discharged from the Pain clinic, after 3 months, when pain was mild (VAS <30 mm).

Fig. 1 
          Pain, documented by the visual analogue scale (VAS). Data are presented as median, interquartile range; *P < 0.05, significant difference compared with baseline.
Fig. 1

Pain, documented by the visual analogue scale (VAS). Data are presented as median, interquartile range; *P < 0.05, significant difference compared with baseline.

Piriformis muscle depth measured with the needle was a mean of 6.7 ± 1.3 cm.

Our study shows that a perisciatic injection using simple landmarks and utilizing a nerve stimulator to locate and inject near the sciatic nerve and into the piriformis muscle is a quick, simple, economical and effective technique and can be considered an alternative to infiltration guided by fluoroscopy or CT.


DOI of refers to article: http://dx.doi.org/10.1016/j.sjpain.2012.05.072.



Servicio de Anestesia, Hospital Meixoeiro, Complexo Hospitalario Universitario de Vigo, Meixoeiro sn, 36200 Vigo-Pontevedra, Spain. Tel.: +34 986811772.

This research was presented as a poster discussion at the “Pain In Europe”, 7th Congress of the European Federation of IASP Chapters (EFIC) 2011 in Hamburg, Germany, September 22, 2011.


  1. Conflicts of interest: None of the authors have conflicts of interest to declare.

References

[1] Benzon HT, Katz JA, Benzon HA, Iqbal MS. Piriformis syndrome: anatomic considerations, a new injection technique, and a review of the literature. Anesthesiology 2003;98:1442–8.Search in Google Scholar

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[3] Fishman SM, Caneris OA, Bandman TB, Audette JF, Borsook D. Injection of the piriformis muscle by fluoroscopic and electromyographic guidance. Reg Anesth Pain Med 1998;23:554–9.Search in Google Scholar

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[5] Smith J, Hurdle MF, Locketz AJ, Wisniewski SJ. Ultrasound-guided piriformis injection: technique description and verification. Arch Phys Med Rehabil 2006;87:1664–7.Search in Google Scholar

[6] Peng PW, Narouze S. Ultrasound-guided interventional procedures in pain medicine: a review of anatomy, sonoanatomy, and procedures: part I: nonaxial structures. Reg Anesth Pain Med 2009;34: 458–74.Search in Google Scholar

Published Online: 2012-07-01
Published in Print: 2012-07-01

© 2012 Scandinavian Association for the Study of Pain

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